We will continue to use immunocytochemical procedures to better define the gonadotrophic cells of the rat anterior pituitary gland. We plan also to label newly synthesized FSH and LH with tritium labeled carbohydrates such as glucosamine or neuraminic acid. Sections of the anterior pituitary will then be studied by radioautography in order to localize the newly formed hormones. By counting silver grains over secretory granules in the gonadotrophs it should be possible to differentiate granules containing FSH from those containing LH. In addition, efforts will be made to establish clonal lines of pituitary cells which secrete specific hormones. Particular emphasis will be given to the development of a clonal line of prolactin secreting cells. The secretory activities of the cell cultures will be monitored by radioimmunoassay of the culture media. The morphology of established clonal lines will be studied by light and scanning electron microscopy.